1,721,001 research outputs found
EXTERNAL-CAVITY LASER DEVICE, CORRESPONDING SYSTEM AND METHOD
No full textA laser device (100), comprising: a source of electromagnetic radiation (S) that comprises at least one reflecting surface (RS), said source (S) being configured to generate a light beam that follows an optical path (OPa; OP) external to said source (S); a dispersive stage (6) located outside said source (S) along said optical path (OP) of said light beam generated by said source (S), said dispersive stage (6) comprising at least one axis of reflection that forms an angle (Θ; cp) with said optical path (OPa; OP) of said light beam and being configured to reflect: at least a first spectral portion of said light beam generated by said source (S) towards said source (S); and a second spectral portion of said light generated by the source (S) along said axis of reflection, wherein said at least one reflecting surface (RS) and said dispersive stage (6) form at least one variable-length external optical cavity (RS, L, 6); at least one collimating lens (C) located along said optical path (OPa; OP) and configured to collimate said light beam coming from said source (S); a collimator module (3), in which said source (S) and said at least one collimating lens (C) are mounted; and an actuator (24) configured to vary a length (L) of said a variable-length external optical cavity (RS, L, 6). In said device: said actuator (24) is mechanically coupled to said collimator module (3); and said actuator (24) is configured to vary the length (L) of said at least one external optical cavity of the variable-length gain medium (RS, L, 6) by moving said collimator (3)
Quantum Transport through a Tonks-Girardeau Gas
No full textWe investigate the propagation of spin impurity atoms through a strongly interacting one-dimensional Bose gas. The initially well localized impurities are accelerated by a constant force, very much analogous to electrons subject to a bias voltage, and propagate as a one-dimensional impurity spin wave packet. We follow the motion of the impurities in situ and characterize the interaction induced dynamics. We observe a very complex nonequilibrium dynamics, including the emergence of large density fluctuations in the remaining Bose gas, and multiple scattering events leading to dissipation of the impurity's motion
Realization of universal optimal quantum machines by projective operators and stochastic maps
No full textOptimal quantum machines can be implemented by linear projective operations. In the present work a general qubit symmetrization theory is presented by investigating the close links to the qubit purification process and to the programmable teleportation of any generic optimal antiunitary map. In addition, the contextual realization of the N-->M cloning map and of the teleportation of the N --> (M-N) universal-NOT (UNOT) gate is analyzed by a very general angular momentum theory. An extended set of experimental realizations by state symmetrization linear optical procedures is reported. These include the 1-->2 cloning process, the UNOT gate and the quantum tomographic characterization of the optimal partial transpose map of polarization encoded qubits
A Littrow-type diode laser with independent control of cavity length and grating rotation
No full textWe present our patented extended-cavity diode laser (ECDL) based on a modified Littrow configuration. Here, the coarse wavelength adjustment via the rotation of a diffraction grating is decoupled from the fine tuning of the external cavity modes by positioning a piezoelectric transducer behind the diode laser. As a result, the fine adjustment of the laser frequency with the piezo does not affect neither the optical feedback alignment nor the broader grating frequency selection curve, resulting in a better mode-hop stable performance compared to the one of standard Littrow ECDLs without optimized pivotal point. We characterize the design and show that it is well suited to atomic and molecular experiments demanding a high level of stability over time and for long cavities ECDLs
Quantum cloning and universal NOT gate by teleportation
No full textThe universal optimal quantum cloning machine (UOQCM) and the universal NOT gate can be implemented contextually by modifying the quantum state teleportation network. We report the experimental realization of the probabilistic UOQCM with polarization encoded qubits. This is achieved by combining on a symmetric beam-splitter the input qubit with an ancilla in a fully mixed state
Experimental realization of the quantum universal NOT gate
No full textIn classical computation, a 'bit' of information can be flipped (that is, changed in value from zero to one and vice versa) using a logical NOT gate; but the quantum analogue of this process is much more complicated. A quantum bit (qubit) can exist simultaneously in a superposition of two logical states with complex amplitudes, and it is impossible to find a universal transformation that would flip the original superposed state into a perpendicular state for all values of the amplitudes. But although perfect flipping of a qubit prepared in an arbitrary state (a universal NOT operation) is prohibited by the rules of quantum mechanics, there exists an optimal approximation to this procedure. Here we report the experimental realization of a universal quantum machine that performs the best possible approximation to the universal NOT transformation. The system adopted was an optical parametric amplifier of entangled photon states, which also enabled us to investigate universal quantum cloning
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